Wireless mesh networks (WMNs) are emerging as attractive solutions for last-mile broadband Internet access. A wireless mesh network is generally composed of wireless clients, a gateway portal that connects the mesh network to the Internet, and the mesh nodes that form the backbone. The mesh nodes wirelessly communicate with each other to provide Internet connectivity for the clients. Routes between the mesh nodes could be multihop.
WMNs aim to provide high-speed Internet service without costly network infrastructure deployment and maintenance. The main obstacle in achieving high-capacity wireless mesh networks is interference between the mesh links. However, estimating interference in multihop wireless links is a difficult task.
It has been proposed that interference may be estimated based on the distance between the nodes. However, measurement results show that distance does not have a strong correlation with the quality of wireless links. One reason is the asymmetric carrier sense (CS) relationship between nodes. That is, one sender senses the other sender's transmission but not vice versa, which may result in one node dominating the link. Another reason is the well known hidden interference or hidden node problem. The IEEE 802.11 standard suggests the use of RTS/CTS to solve the hidden interference problem. However, the RTS/CTS mechanism has been shown to be ineffective in eliminating the hidden node problem and fails to increase the multihop capacity of the link.
Link Interference Ratio (LIR) and Broadcast Interference Ratio (BIR) are measurement-based, instead of distance-based, schemes that estimate interference between two wireless links that do not share end-points. Both LIR and BIR, with different measurement complexities, estimate the amount of pairwise link interference. However, both BIR and LIR only indicate the aggregate throughput of the receivers for the two links in the presence of interference. BIR and LIR do not provide information on each link's throughput. Thus, situations where the aggregate throughput of two links is satisfactory but the throughput of one of the links is poor may not be detected when relying solely on BIR or LIR.